1. Field of the Invention
The present invention relates to a Radio Frequency Identification (RFID) tag and a use of such a RFID tag.
2. Description of Related Art
RFID tags are currently in widespread use, inter alia as security features. There are proposals to equip banknotes, credit cards, debit cards, store loyalty cards and other high-value objects with RFID tags in an attempt to prevent fraud.
The present inventor has appreciated that there may be privacy and security concerns if the objects listed above (in the following referred to as high-value objects) are equipped with a RFID tag. For example, whilst embedding a RFID tag in a banknote would enable the identity and authenticity of the banknote to be verified by a suitable RFID reader, it might also enable a criminal who is in the possession of a suitable RFID reader to detect whether a particular person is carrying a large amount of money. This would, of course, be undesirable.
The present invention has been made to address this concern.
Aspects of the present invention are set out in the independent claims.
In one aspect the present invention provides a Radio Frequency Identification (RFID) tag comprising:                an electronic identification circuit coupled to an antenna, wherein the RFID tag is arranged to communicate with a RFID tag reader via said antenna, using RF energy, and        means sensitive to light for inhibiting communication between the RFID tag reader and the RFID tag.        
The means sensitive to light (for example a photodiode, a phototransistor, a photocell or a solar cell) can ensure that the RFID tag can only be read when exposed to (sufficient) light, for example ambient light. Conversely, when the RFID tag is not exposed to (sufficient) light, e.g. if the tag is embedded in a banknote and the banknote is placed in a wallet, the RFID tag cannot be read by a RFID reader.
The electronic identification circuit may be powered by RF energy received via the antenna, or alternatively it may be powered by a source of energy other than the antenna, for example a battery. Preferably, the means sensitive to light is arranged to reduce the range over which said RFID tag can transmit information to said reader in the absence of light of more than a predetermined threshold. Such an arrangement can be of use if it is desired to enable legitimate use of a high-value object despite the absence of light when the high-value object is brought into close proximity to a RFID tag reader. For example, it may be desirable for a credit card carrying the tag to be used for payment even if the credit card remains in a wallet. The tag could be configured such that it can be read (even in the absence of light) over a distance of a few millimeters or centimeters. Detection of the credit card by criminals could still be prevented as they are less likely to be able to bring a RFID tag reader into such close proximity to a potential victim's wallet.